If you can bear to part out an Ampex speaker-amp, you have a great starting point for an excellent
infinite-baffle system. The speaker in that little cabinet has a lot of extension ability and if
it's mounted in a shallow closet's door, for instance, it puts out a LOT of bass and a lot of volume
with that little 10W tube amp, or so I've been told. The early red-vinyl cases contained speakers
designed by James Lansing and built by Ampex itself. Later models have different (but better
lower-bass) speakers made by JBL for Ampex.
-- Tom Fine
----- Original Message -----
From: "Randy A. Riddle" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, February 08, 2013 8:35 PM
Subject: Re: [ARSCLIST] Passive radiator loudspeaker was Mono but Out-of-Phase
> Reminds me of the prof in my college Physics of Sound course that
> brought this tiny little speaker - a common 1" or so thing from a
> transistor radio - into class one day, saying it was his great new
> hi-fi. He plugged it in and, of course, you could barely hear it at
> Then he walked into another room and brought out this huge circle made
> of plywood that was about as tall as he was with a tiny hole in the
> center. He placed the speaker in the hole and - voila - nice hi-fi
> On Fri, Feb 8, 2013 at 6:42 PM, Michael Biel <[log in to unmask]> wrote:
>> From: Don Cox <[log in to unmask]>
>>>>> Electrostatic speakers have no enclosure. They are not infinite baffle
>>>>> unless installed in a will.
>>>>> Infiniet baffle is a technical term that means none of the sound from
>>>>> the back comes to a listener in the front.
>> On 08/02/2013, Lou Judson wrote:
>>>> Strictly speaking, yes. However, a large baffle can be very near to
>>>> infinite in practice. Frequencies down to about 80 Hz can be controlled,
>>>> and below that, in most living rooms there are so many complications from
>>>> room effects that it is hard to say what is happening to the sound.
>>>> For example, in my teen years I put speakers in the walls of the
>>>> living room that had the attic behind them. Infinite baffle. No front
>>>> vents. <L>
>> I used to describe it in class by pretending to mount a driver on the
>> classroom door. If the door was open there would be cancellation of the
>> front and back waves. Close the door and we hear only the front -- and
>> annoy everyone in the hall. Now, if the door is not sealed at the
>> bottom, the slot is the bass reflex opening. If you want a round hole,
>> remove the door lock. In an old building if there was a transom above
>> the door, we could tune the opening. Now if we open a window and the
>> classroom next door have their door and windows open, that could be a
>> labyrinth reflex opening (Bose???)
>> I sometimes used a closet to explain acoustic suspension speakers since
>> we could "seal" a closet. Then I dragged in a horn tweeter from an
>> Altec A-7 and blew their minds telling them that this huge heavy
>> cast-iron monster was a tweeter. Then came the explanation of the horn,
>> and the horn/labyrinth reflex woofer mounting of the A-7.
>>> Strictly speaking, unless your attic was infinite in volume, this is
>>> another "large baffle".
>> I also discussed mounting the driver on a window, then the great
>> outdoors was a real infinite baffle!
>>> And can one speaker act as a passive cone for
>>> the other (if the big drum is all in one channel, for instance) ?
>>> Don Cox [log in to unmask]
>> In my case I was in mono! But in discussing multi-driver systems I
>> explained that the backs of the other drivers had to be sealed or in a
>> separate box so that they are not affected by the rear compressions of
>> the woofer.
>> Mike Biel [log in to unmask]